(1) Field of the Invention:
This invention relates to a process for preparing a printed-circuit board, and more particularly to the improvement which comprises applying a corrosion preventing treatment with a specified corrosion inhibitor to a printed-circuit copper-clad base plate prior to subjecting the printed-circuit copper-clad base plate to an electrodeposition coating, resulting in preventing the eluation of copper from the printed-circuit copper-clad base plate upon effecting the electrodeposition coating, thereby preventing such phenomena as incomplete developing onto the printed-circuit board, with the further results of completely protecting the corners and interior of through-holes, and preparing a precise printed-circuit board.
(2) Description of the Prior Art:
The process for preparing a printed-circuit board, which comprises coating a photosensitive electrodeposition coating composition onto a printed-circuit base plate, is known (see, for example, U.S. Pat. Nos. 3954587, 4592816, 4632900 and 4673458; Japanese Patent Application Laid-Open Nos. 207139/85, 206293/86 and 6070/88, etc.).
The process for preparing a printed-circuit board according to the electrodeposition coating process has such advantages that automation is made possible, that a uniform film is obtained and so forth, and it is an industrially advantageous process. However, corrosion of the printed-circuit base plate at the time of carrying out the electrodeposition coating cause abnormal depositing of the film onto the corroded area or the failure of forming the film onto the corroded area, resulting in abnormal phenomena which may take place at the time of developing. Particularly, in the case of preparing a precise pattern, various phenomena such as disconnection, deficiency of pattern, shortcircuiting and the like may take place, resulting in defective printed-circuit boards.